1. Technical Field
The present invention relates to controlling a damper in a vehicle suspension system, and is particularly directed to an apparatus for controlling a rotary damper in a vehicle suspension system.
2. Background Art
Damping devices for use in vehicle suspension systems are known. One type of damping device for use in a vehicle suspension system is a rotary shock absorber. An example of a rotary shock absorber is disclosed in U.S. Pat. No. 4,942,947. The rotary shock absorber of U.S. Pat. No. 4,942,947 includes a field-responsive fluid disposed in a chamber defined within the rotary shock absorber. A number of energizeable electromagnetic coils are provided for, when energized, applying an energy field to the fluid in the chamber. The shear resistance of the fluid varies as a function of the energy field acting on the fluid. The angular movement of a rotor blade in the chamber is resisted by the fluid. The resistance to movement of the rotor blade in the chamber varies as a function of the shear resistance of the fluid. Therefore, the resistance to movement of the rotor blade in the chamber varies as a function of the energy field applied to the fluid in the chamber.
Control systems for controlling the damping rate of a damper device are also known. Typically, such a control system provides a damping control signal which, at any given moment in time, varies as a function of a sensor signal from one of a plurality of remote sensors attached to the vehicle. The sensor signals from the remote sensors are indicative of road and vehicle conditions encountered or to be encountered by the vehicle. As an example, a plurality of remote sensors may include an accelerometer for sensing the acceleration of the vehicle relative to ground and for providing a sensor signal indicative thereof. A control unit, such as a microprocessor, receives the sensor signals from the remote sensors. The microprocessor processes the sensor signals from the remote sensors in accordance with a preprogrammed procedure stored in an internal memory of the microprocessor and provides a damping control current signal for controlling the damping rate of the damper device.
In prior known control systems for controlling the energy field applied to a damper device, the microprocessor at any given moment in time is responding to the sensor signal from only one of the plurality of remote sensors to provide the damping control current signal for controlling the damping rate of the damper device. Also, in prior known control systems, the energy field is applied in a manner to a damper device so that either only a hard mode or only a soft mode of control of the damper device is effected at any given moment in time.